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- Author or Editor: Cícero Aragão x
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Abstract
Rifampicin–Isoniazid mixture is a frequently used product in the treatment of tuberculosis. Rifampicin exhibits polymorphism and exists in two polymorphic forms: the stable form I and the metastable form II. The aim of this work was to evaluate the thermal behavior of the binary mixtures of polymorphs I and II of rifampicin and isoniazid by using DSC. Mixtures of different forms (rifampicin form I and II) showed interaction with isoniazid indicating that the mixtures are less stable compared to the drug alone. Interaction was observed in case of both polymorphs of rifampicin.
Abstract
Warifteine and methylwarifteine are bisbenzylisoquinoline alkaloids from Cissampelos sympodialis Eichl., produces a reversible, nonspecific, and noncompetitive antagonism of histamine, anti-allergic therapy, and used in the folk medicine for the treatment of airway respiratory diseases. Thermal techniques are used for several purposes, e.g., for thermal characterization, and measurement of the vapor pressure with objective of the quantitative determination. The objective of this study was to evaluate of the vapor pressure of the curves of warifteine and methylwarifteine by thermogravimetry analysis, how a fast and sensible method for quantitative determination. This method is based on the ratio of the Arrhenius, Langmuir, and Antoine equations for a reference material and the sample under investigation. The results showed these alkaloids follow zero-order kinetics with respect to volatilization. The vapor pressure curves of warifteine and methylwarifteine were plotted for the rates of 10, 15, and 20 °C min−1. The proposed method also possesses the potential.
Abstract
Worldwide Brazil is among one of the 22 countries with high rates of tuberculosis placing this disease as a priority for the Government Health Policies in this country. Studies with the main tuberculostatic drugs rifampicin, isoniazid, pyrazinamide, and ethambutol, aiming the development of fixed-dose combination formulations (FDCs) have been performed. The aim of this study was to evaluate the thermal behavior of these drugs by DSC, TG/DTG, and DTA in order to predict possible physical and chemical interactions between tuberculostatics. DSC and DTA curves suggested incompatibility and/or interactions among drug preparations resulting from new thermal events, as well as the disappearance and shift of the melting point of the drugs. TG/DTG curves of drug mixtures presented different profiles from those observed for the individually tested drugs, supporting the evidence of drug incompatibility and indicating that mixtures are less stable when compared to the drugs alone.
